Structure guidance and drive assembly for translation of a robotic picker assembly

ABSTRACT

A structure, guidance, and drive assembly for translation of a robotic picker assembly may comprise a support frame having a front end, a rear end, and two opposed sides. The front and rear ends of the support frame are positioned in parallel, spaced-apart relation to a lateral axis, while the two opposed sides are positioned in parallel, spaced-apart relation to a longitudinal axis, the lateral and longitudinal axes defining a horizontal reference plane. The support frame includes a first elongate bearing surface that is located at about the front end of the support frame. The first elongate bearing surface extends between the two opposed sides of the support frame so that the first elongate bearing surface extends in a direction that is substantially parallel to the lateral axis and lies in a first bearing plane that is substantially parallel to the horizontal reference plane. The support frame also includes a second elongate bearing surface that is located at about the rear end of the support frame. The second elongate bearing surface also extends between the two opposed sides of the support frame and also extends in a direction that is substantially parallel to the lateral axis and lies in a second bearing plane that is substantially parallel to the horizontal reference plane. The second bearing surface plane is non-coplanar with the first bearing surface plane. A three point contact primary bearing system mounted to the robotic picker assembly is adapted to engage the first and second elongate bearing surfaces and allows the robotic picker assembly to be displaced within the support frame in a direction generally parallel to the lateral axis and along the horizontal reference plane. An actuator connected to the robotic picker assembly moves the robotic picker assembly to predetermined points along the lateral axis in response to commands from a control system.

BACKGROUND

The present invention relates generally to systems for handling andstoring media cartridges such as optical disk or tape cartridges and,more particularly, to apparatus for moving a cartridge picker assemblyto a predetermined cartridge engagement location.

An optical disk is a data storage medium which is readable by alaser-based reading device. Optical disks known as "compact disks" or"CDs" have become increasingly popular during the last decade forrecording music and audio-visual works. Due to the large storagecapacity of optical disks as compared to conventional magnetic storagemedia, optical disks known as "ROM disks" have become popular forstoring computer readable information. However, until very recently,optical disks were of somewhat limited use in the computer industry dueto the fact that optical disks could not be erased and written with newinformation, i.e., ROM disks are "read only" memory devices. However,recent technology has produced optical disks which are both computerreadable and computer writable. Consequently, optical disks are becomingincreasingly important in the computer industry and may eventuallyreplace magnetically readable and writable storage media such as floppydisks and hard disks. Another recent development, the ability to providedata storage on both surfaces on an optical disk, has effectivelydoubled the storage capacity of the optical disk. Optical disks of thetype used in computer applications are generally mounted inparallelepiped-shaped cartridges. Also used in the computer industry fordata storage are parallelepiped-shaped tape cartridges such as DigitalAudio Tape (DAT) cartridges and 8 mm tape cartridges.

The increasing popularity of such data storage cartridges in thecomputer field has spurred the development of many different types ofautomated cartridge handling systems for storing the cartridges at knownlocations and for retrieving a desired cartridge from a storage locationand inserting the cartridge into a cartridge reading device, such as atape or disk drive. Generally speaking, such a cartridge handling systemmay include a cartridge storage system for storing the cartridges atcorresponding storage locations and a cartridge engaging assembly forretrieving a desired cartridge from its corresponding storage location,transporting the cartridge to a cartridge reading device, such as a diskor tape drive, and inserting the cartridge into the drive. The cartridgeengaging assembly may also remove a cartridge from a drive, move thecartridge into alignment with its storage location, and return thecartridge to its storage location.

Various features and components of cartridge handling systems andcartridge engaging assemblies are disclosed in U.S. Pat. Nos. 4,944,082for METHOD OF PROVIDING A SHEET METAL HOUSING WITH PRECISELY POSITIONEDMOUNTING REFERENCES of Jones et al.; 4,998,232 for OPTICAL DISK HANDLINGAPPARATUS WITH FLIP LATCH of Methlie et al.; 5,014,255 for OPTICAL DISKCARTRIDGE HANDLING APPARATUS WITH PASSIVE CARTRIDGE ENGAGEMENT ASSEMBLYof Wanger, et al.; 5,010,536 for CARTRIDGE HANDLING SYSTEM of Wanger etal.; 5,043,962 for CARTRIDGE HANDLING SYSTEM of Wanger, et al.;5,062,093 for OPTICAL DISK INSERTION APPARATUS of Christie, et al.;5,101,387 for LATERAL DISPLACEMENT CONTROL ASSEMBLY FOR AN OPTICAL DISKHANDLING SYSTEM of Wanger, et al.; 5,184,336 for LATERAL DISPLACEMENTCONTROL ASSEMBLY FOR AN OPTICAL DISK HANDLING SYSTEM of Wanger, et al.;5,596,556 for LINEAR DISPLACEMENT AND SUPPORT APPARATUS FOR USE IN ACARTRIDGE HANDLING SYSTEM of Luffel, et al.; and 08/558,949 filed Oct.12, 1993 for CARTRIDGE HANDLING SYSTEM WITH DUAL CARTRIDGE ENGAGINGASSEMBLY, which are each hereby specifically incorporated by referencefor all that is disclosed therein.

Many cartridge handling systems of the type described above store thecartridges in a two-dimensional array consisting of one or more verticalcolumns and horizontal rows. One or more disk or tape drives for thecartridges may be located anywhere in the array, but are usuallypositioned at the ends of the columns or rows. In any event, such acartridge handling system will include apparatus for moving thecartridge engaging assembly throughout the array, so that the storedcartridges can be accessed and transported to and from the appropriatedisk or tape drive.

While cartridge handling systems of the type described above provide aconvenient means for automatically accessing a large number ofcartridges, they are not without their problems. For example, a keyfactor in the successful operation of such a cartridge handling systemis the ability to quickly and accurately move the cartridge engagingassembly throughout the array, engage a desired cartridge, and move itquickly to the appropriate cartridge reading device. Generally speaking,the apparatus for so moving the cartridge engaging assembly tends to becomplex, and may include a large number of drive motors and positionsensors to accomplish the desired functions. As with any mechanicalsystem, however, such increased complexity often means decreasedreliability. Therefore, it is desirable to minimize the number ofcomponents in such a system, but without sacrificing other performanceparameters, such as speed and accuracy.

Another problem with such cartridge handling systems relates to thesupport and accurate positioning of the cartridge engaging assembly withrespect to the cartridges stored in the array. For example, manycartridge engaging assemblies are cantilevered on a leadscrew, whichwhen turned, moves the cartridge assembly across the array ofcartridges. Unfortunately, such a cantilevered mounting arrangementtends to allow excessive transverse or rotational movement of thecartridge engaging assembly, which reduces positional accuracy. One wayto increase the stability of the cartridge engaging assembly, thuspositional accuracy, is to use rigid guide rails or tracks to provideadditional support to the cartridge engaging assembly.Disadvantageously, many of the guide rail or track assemblies in usetoday are precision machined items, which adds to the overall cost ofthe cartridge handling system. Further, such guide rail assemblies areoften difficult and time consuming to align. Worse yet, the guide railassembly may be knocked out of alignment during subsequent shipping ormovement of the cartridge handling device, thus requiring re-alignmentand re-calibration before the device can be placed in operation.

Another problem relating to many cartridge handling systems is accessspeed, and efforts are constantly being made to minimize the mass ofeach component of the system, including the linear displacement andsupport apparatus for the cartridge engaging assembly, which tends toincrease the speed at which the cartridge engaging assembly may be movedamong the columns and rows of cartridges. Unfortunately, it is usuallymore difficult to achieve the desired degree of positional accuracy witha lighter weight system, and designers are constantly trying to find theoptimum balance between light weight and positional accuracy. It is alsodesirable to minimize the volume requirements of the linear displacementand support apparatus so that it may be mounted in a relatively smallspace within the cartridge handling system.

Consequently, there remains a need for a cartridge handling systemhaving increased positional accuracy to reduce errors due tomisalignment of the cartridge engaging assembly. Such increasedpositional accuracy should be achieved with a minimum number ofcomponents to increase reliability, yet not require the use of expensivemachined guide rails or tracks, which adds cost. Additional advantagescould be realized by reducing the amount of time required to align andcalibrate the assembly during production, and by reducing the likelihoodof subsequent misalignment, such as may occur during shipping. Ideally,the above advantages should be accomplished without increasing the massof the moving components, which tends to adversely affect access speed.

SUMMARY OF THE INVENTION

The structure, guidance, and drive assembly for translation of a roboticpicker assembly may comprise a support frame having a front end, a rearend, and two opposed sides. The front and rear ends of the support frameare positioned in parallel, spaced-apart relation to a lateral axis,while the two opposed sides are positioned in parallel, spaced-apartrelation to a longitudinal axis, the lateral and longitudinal axesdefining a horizontal reference plane. The support frame includes afirst elongate bearing surface that is located at about the front end ofthe support frame. The first elongate bearing surface extends betweenthe two opposed sides of the support frame so that the first elongatebearing surface extends in a direction that is substantially parallel tothe lateral axis and lies in a first bearing plane that is substantiallyparallel to the horizontal reference plane. The support frame alsoincludes a second elongate bearing surface that is located at about therear end of the support frame. The second elongate bearing surface alsoextends between the two opposed sides of the support frame and alsoextends in a direction that is substantially parallel to the lateralaxis and lies in a second bearing plane that is substantially parallelto the horizontal reference plane. The second bearing surface plane isnon-coplanar with the first bearing surface plane. A three point contactprimary bearing system mounted to the robotic picker assembly is adaptedto engage the first and second elongate bearing surfaces and allows therobotic picker assembly to be displaced within the support frame in adirection generally parallel to the lateral axis and along thehorizontal reference plane. An actuator connected to the robotic pickerassembly moves the robotic picker assembly to predetermined points alongthe lateral axis in response to commands from a control system.

BRIEF DESCRIPTION OF THE DRAWING

Illustrative and presently preferred embodiments of the invention areshown in the accompanying drawing in which:

FIG. 1 is a perspective view of a cartridge handling system having thestructure, guidance, and drive assembly for the translation of a roboticpicker assembly according to the present invention;

FIG. 2 is a perspective view of the structure, guidance, and driveassembly showing the robotic picker assembly frame at a first endposition;

FIG. 3 is a perspective view of the underside of the structure,guidance, and drive assembly more clearly showing the engagement of thesixth roller assembly with the outer surface of the vertical bearingmember;

FIG. 4 is a perspective view of the frame assembly showing the detailsof the position indexing aperture and slots of the position encoderassembly;

FIG. 5 is a cross-section view in elevation of the frame assembly takenalong the line 5--5 of FIG. 4;

FIG. 6 is a plan view of the structure, guidance, and drive assemblyshowing the position of the first, second, third, fourth, and fifthroller assemblies;

FIG. 7 is a cross-section view in elevation of the structure, guidance,and drive assembly taken along the line 7--7 of FIG. 6 more clearlyshowing the sixth roller assembly and the spring biasing member;

FIG. 8 is a plan view of the structure, guidance, and drive assemblyshowing the motor and drive cable assembly; and

FIG. 9 is a perspective view of the structure, guidance, and driveassembly and motor and drive cable assembly.

DETAILED DESCRIPTION OF THE INVENTION

A structure, guidance, and drive assembly 10 for the translation of arobotic picker assembly 36 is shown in FIG. 1 as it could be used in acartridge handling system 12 for storing and accessing a plurality ofcartridges 28 stored in a plurality of vertical columns 17. Thecartridge handling system 12 may comprise a cartridge storage rackassembly 24 that is mounted to a base plate 14 and a top cover 16. Thecartridge storage rack assembly 24 contains a plurality of cartridgestorage locations or slots 26 arranged in two columns 17 that areadapted to slidably receive the cartridges 28. The cartridge storagerack assembly may also include first and second travel stops 51, 53 forproviding an initial or reference position 27 (shown in phantom inFIG. 1) for a frame assembly 32, as will be described in greater detailbelow. Finally, the cartridge storage rack assembly 24 may also includespace for one or more cartridge readers 30 capable of reading data from,or writing data to, the storage media contained within the cartridges28.

The frame assembly 32 may be slidably mounted to first and second guiderails 18 and 20 so that it can be moved up and down (i.e., along axisYY) by a suitable actuator assembly 34. Frame assembly 32 may be adaptedto receive a robotic picker assembly 36 of the type disclosed in U.S.patent application Ser. No. 08/558,949 for CARTRIDGE HANDLING SYSTEMWITH DUAL CARTRIDGE ENGAGING ASSEMBLY, which was incorporated byreference above, although nearly any type of robotic picker assemblyknown in the art could also be used without departing from the scope ofthe present invention. The particular robotic picker assembly 36identified above is slidably mounted within frame assembly 32, so thatit can be moved back and forth along a lateral axis (i.e., along the ZZdirection) to access cartridges 28 stored in either of the verticalcolumns 17. Consequently, the range of travel of the structure,guidance, and drive assembly 10 is such that the robotic picker assembly36 can access all of the cartridges 28 stored within the cartridgestorage rack 24, as well as the cartridge reader 30.

Referring now to FIG. 2, structure, guidance, and drive assembly 10 mayinclude a picker frame assembly 37 adapted to receive a suitable roboticpicker assembly 36 (not shown in FIG. 2 for clarity). The picker frame37 is mounted within the frame assembly 32 by a primary three pointcontact bearing system that allows the picker frame 36 to be linearlytranslated in the ZZ (i.e., lateral) direction. As will be discussed ingreater detail below, the primary three point contact bearing system maycomprise a first roller assembly 40 mounted to a first side member 44 ofpicker frame assembly 37 and a second roller assembly 42 mounted to asecond side member 48. The first and second roller assemblies 40 and 42are mounted to the respective side members 44 and 48 near the frontmember 46 so that the respective rollers 41 and 43 engage a front guiderail 50 attached to the frame assembly 32. A third roller 52 is attachedto the rear frame member 54 of picker frame 36 and engages a horizontalbearing surface 56, as best seen in FIG. 6.

Still referring to FIG. 6, a secondary three point contact bearingsystem is used to prevent the picker frame 36 from moving in the XX(i.e., longitudinal) direction. More specifically, the secondary threepoint contact bearing system comprises a fourth roller 60 attached tothe rear frame member 54 near the first side member 44 and a fifthroller 62 attached to the rear frame member 54 near the second sidemember 48. The fourth and fifth rollers 60 and 62 engage the inner side38 of vertical bearing member 66 (FIGS. 5 and 6). A sixth rollerassembly 64 is mounted to the rear frame member 54, so that roller 65engages the outer side 68 of vertical bearing member 66, as best seen inFIG. 3. The sixth roller assembly 64 is spring biased against the outerside 68 of vertical bearing member 66 to keep the fourth and fifthrollers 60 and 62 firmly engaged with the inner side of bearing surface38, as will be explained in greater detail below.

The picker frame assembly 37 may be rolled back and forth within frameassembly 32 along the ZZ, or lateral, direction by a motor and drivecable assembly 70, as best seen in FIGS. 8 and 9. Briefly, motor anddrive cable assembly 70 comprises a wire rope or drive cable 72 mountedto the first frame side member 74 and the second frame side member 76 sothat it is stretched therebetween. A tensioning device 79 keeps drivecable 72 at a predetermined tension. Drive cable 72 is wrapped around acapstan 78 connected to a suitable drive motor 80 mounted to the rearframe member 54 of picker frame assembly 37. When drive motor 80 isactuated by a suitable control system (not shown), the engagement of thedrive cable 72 with the capstan 78 will cause the picker frame assembly37 to be rolled from one end of the frame assembly 32 to the other end,i.e., along the ZZ (lateral) direction. The picker frame assembly 37 mayalso include a position encoder 81 (FIG. 7) for determining the positionof the picker frame 37 within the frame 32. In one preferred embodiment,the position encoder 81 includes an optical sensor 82 for sensing anaperture 84 (FIG. 4) and end point indexing slots 83 and 85 in torsionbox 58, as will be described in greater detail below.

A significant advantage of the cartridge engaging assembly 10 accordingto the present invention is that the primary three point contact bearingsystem rollingly supports the robotic picker assembly 36 within frameassembly 32 on a precisely defined horizontal reference plane. Thesecondary three point contact bearing system prevents the robotic pickerassembly 36 from moving in the XX (i.e., longitudinal) direction.Therefore, the combination of the primary and secondary three pointcontact bearing systems allow the picker assembly 36 to be smoothlytranslated along the ZZ (i.e., lateral) direction and along a preciselydefined horizontal reference plane, thus resulting in increasedpositional accuracy.

Another advantage of the present invention is that the increasedpositional accuracy has been achieved without the need to resort toexpensive, precision machined components. In fact, most of thecomponents may be formed from relatively light gauge sheet metal, thusreducing the overall weight of the moving parts as well as reducingproduction costs. The structure also allows for much easier alignmentand calibration during production, and is less likely to becomemis-aligned during subsequent shipping or handling.

Still another advantage of the present invention is that motor and drivecable assembly 70 allow the robotic picker assembly to be moved back andforth within frame assembly 32 while the frame assembly 32 is itselfbeing translated in the vertical direction. This ability to translatethe robotic picker assembly "on the fly" decreases cartridge accesstime.

The details of the frame assembly 32 are best seen by referring to FIGS.4 and 5 simultaneously with occasional reference to FIGS. 2 and 3. Inone preferred embodiment, the frame assembly 32 may be made fromrelatively light gauge (e.g., 18 gauge) sheet metal and fabricatedaccording to the teachings of U.S. Pat. No. 4,944,082 for METHOD OFPROVIDING A SHEET METAL HOUSING WITH PRECISELY POSITIONED MOUNTINGREFERENCES, which was incorporated by reference above. Accordingly, itwill be possible to fabricate frame assembly 32 to close tolerances,thus further increasing positional accuracy. For example, a criticaldimension of one preferred embodiment of the frame assembly 32 may bethe spacing 31 between the vertical bearing member 66 and the attachmentholes 33 for the bearing (not shown) for engaging the second guide rail20 (FIG. 1). Close tolerances for this spacing 31 will help ensureaccurate positioning of the robotic picker assembly 36 along the XXaxis. Another critical dimension is the spacing 35 between the end 39 ofthe front guide rail 50 and the frame side 76. See FIG. 6. Again, closetolerances for the spacing 35 helps to ensure that the end points of thepicker frame assembly 37 will be precisely defined with respect to theend 39 of front guide rail 50, which end 39 engages guide rail 18. Theresulting arrangement provides for more accurate positioning along theZZ axis.

Referring back to FIGS. 4 and 5, frame assembly 32 may comprise aplate-like base member 86 that defines a horizontal reference plane 69.Base member 86 includes a vertical bearing member 66 perpendicular tohorizontal reference plane 69, a horizontal bearing surface portion 56parallel to horizontal reference plane 69, and a vertical end flange 88,as best seen in FIGS. 4 and 5. Horizontal bearing surface 56 includes aclearance slot 90 which allows the sixth roller assembly 64 of thesecondary three point contact bearing system to engage the outer bearingsurface 68 of vertical bearing member 66.

Frame assembly 32 also includes a first side member 74 and a second sidemember 76 that may be integrally formed from the base member 86, or maybe separate components. A front guide rail 50 having a C-shapedcross-section is attached to the base member 86 and is adapted to engagethe first and second roller assemblies 40, 42 of the primary three pointcontact bearing system. For increased positional accuracy, the frontguide rail 50 may be integrally formed from base member 86, although itcould also comprise a separate piece.

A torsion box 58 having an L-shaped cross-section may be attached to thevertical bearing member 66 and the base member 86 by any convenientmeans, such as by welding, to increase the torsional rigidity of theframe assembly 32. Torsion box 58 also includes a position indexingsystem comprising an encoder aperture 84 having a first end 94 and asecond end 96, as well as a pair of end point indexing slots 83, 85,which allow the optical sensor 82 to assist in positioning the pickerframe assembly 37 at the respective end travel points. Torsion box 58also includes a clearance slot 71 for the optical sensor 82, as bestseen in FIG. 7. Torsion box 58 may also be manufactured from a singlepiece of sheet metal.

The robotic picker assembly 36 (FIG. 1) may be mounted in suitablepicker frame assembly 37 that is slidably mounted within frame 32. Thedetails of the picker frame assembly 37 are best seen by referring toFIGS. 2 and 3 simultaneously with occasional reference to FIGS. 6, 7, 8,and 9. As was mentioned above, picker frame assembly 37 is adapted toreceive the particular cartridge picker assembly 36 (FIG. 1) that willbe used for releasably engaging the cartridges 28. While the specificdetails of the picker frame assembly 37 may differ depending on theparticular robotic picker assembly used, it will generally include afirst side member 44 and a second side member 48 separated at one end bya front member 46 and at the other end by a rear frame member 54. Thefirst roller assembly 40 and the second roller assembly 42 are mountedto the respective first and second side members 44, 48, near the frontmember 46, so that the respective rollers 41 and 43 engage the C-shapedguide rail 50 of frame assembly 32, as best seen in FIGS. 3 and 7. Thethird roller 52 is mounted to the rear frame member 54, substantiallyequidistant between the first and second side members 44, 48, so that itengages horizontal bearing surface 56, as best seen in FIGS. 6 and 7.

As was mentioned above, the first, second, and third roller assemblies40, 42, and 52 form the three point contact primary bearing system thathorizontally positions the picker frame assembly 37 within frameassembly 32 and allows it to be rolled in the ZZ (i.e., lateral)direction. Since only three contact points are used, the picker frameassembly 37 will roll substantially on the horizontal reference plane69. That is, the first and second roller assemblies 40 and 42 roll alongguide channel 50, which is coincident with horizontal reference plane69, while the third roller 52 rolls along horizontal surface 56 which issubstantially parallel to the horizontal reference plane 69. Thus, theentire picker frame assembly 37 will translate along the horizontalreference plane 69.

Vertical positioning accuracy of the robotic picker assembly 36 withrespect to the cartridges 28 is enhanced if the frame assembly 32 isused in a cartridge handling system 12 that includes integral travelstops 51 and 53. That is, if the frame assembly 32 is lowered to theinitial or home position 27 (FIG. 1) so that the front guide rail 50 isresting on the travel stops 51, 53 (see FIG. 5), then only the thickness57 of front guide rail 50 will separate the horizontal reference plane69 from the travel stops 51, 53. Thus, the initial reference position ofthe robotic picker assembly 36 can be accurately determined.

Further, the first and second roller assemblies 40 and 42, beingpositioned at the front corners of the picker frame 36, substantially atthe intersection of the front member 46 with the first and second sidemembers 44 and 48, maintain the parallel alignment of the front member46 with the horizontal guide rail 50 throughout the range of travel ofthe picker frame assembly 37, thus reducing cartridge engaging problemsdue to misalignment of the robotic picker assembly 36 (FIG. 1) with thecartridges 28.

The picker frame assembly 37 is prevented from moving in XX (i.e.,longitudinal) direction by the three point secondary bearing systemwhich engages the inner and outer bearing surfaces 38 and 68 of verticalbearing member 66. See FIGS. 3, 6, and 7. The three point secondarybearing system includes a fourth roller 60 mounted to the first sidemember 44 of picker frame assembly 36 and a fifth roller 62 mounted tothe second side member 48, so that they engage the inner bearing surface38 of vertical bearing member 66. The sixth roller assembly 64 ismounted to the rear frame member 54, substantially equidistant betweenthe first and second side members 44, 48, so that roller 65 engages theouter bearing surface 68 on the opposite side of vertical bearing member66 through the clearance slot 90, as best seen in FIGS. 3 and 7. Thesixth roller assembly 64 is pivotally mounted to the rear frame member54 along pivot axis 98 and includes a spring 91 for biasing the sixthroller assembly 64 against bearing surface 68 to keep the fourth andfifth rollers 60 and 62 firmly engaged with inner bearing surface 38.

The picker frame assembly 37 is rolled back and forth within the frameassembly 32 by motor and drive cable assembly 70 as best seen in FIGS.7, 8, and 9. As was described above, the motor and drive cable assembly70 comprises a wire rope or drive cable 72 mounted between the firstframe side member 74 and the second frame side member 76. A tensioningdevice 79 mounted to one end of drive cable 72 keeps drive cable 72 at apredetermined tension. The drive cable 72 is wrapped around the capstan78 of drive motor 80, which itself is mounted to the rear frame member54. When drive motor 80 is actuated by a suitable control system (notshown), the engagement of the drive cable 72 with the capstan 78 willcause the picker frame assembly 36 to be rolled along the ZZ direction.In one preferred embodiment, drive cable 72 is wrapped only once aroundcapstan 78, which allows the drive cable to slip on the capstan 78 inthe event the picker assembly becomes jammed, thus preventing damage tothe motor 80 and/or the motor control system (not shown).

Since the capstan 78 attached to drive motor 80 may slip along the drivecable 72 under certain circumstances, a position encoder assembly 81 isused to determine the position of the picker frame assembly 37 withrespect to the frame assembly 32. In one preferred embodiment, theposition encoder assembly 81 may comprise an optical sensor 82 fordetecting the aperture 84 and pair of end point indexing slots 83 and 85that are integral to torsion box 58, as best seen in FIGS. 4 and 7. Eachend point indexing slot 83, 85 is positioned a spaced distance from therespective ends 94, 96 of aperture 84, as best seen in FIG. 4. While awide variety of control algorithms are well-known in the art that couldbe used with the encoder 81, one preferred embodiment utilizes analgorithm that functions as follows.

Suppose, for example, that the picker frame assembly 37 is located withrespect to the frame assembly 32 as shown in FIG. 8. The picker frameassembly 37 is held against frame side 74 by motor 80, which applies alow level holding torque to capstan 78, which holds the picker frame 37firmly against frame side 74. So located, the robotic picker assembly 36will be aligned with the right hand column 17, as shown in FIG. 1, andthe optical sensor 82 will be positioned just to the left of end slot 83(FIG. 4). If it is desired to move the robotic picker assembly 36 toalign it with left hand column 17 (FIG. 1), then the motor controlassembly (not shown) would actuate motor 80 to apply maximum torque inthe reverse direction, which will begin moving the picker frame assembly37 in the direction of arrow 92 (FIG. 8). Maximum motor torque wouldcontinue to be applied until the optical sensor 82 detects the secondend 96 of aperture 84 (FIG. 4). At this point, the control system wouldthen reduce the motor torque to slow the picker frame 37 until theoptical sensor 82 detects end point indexing slot 85. At this point, themotor control system will apply a small holding voltage to motor 80,which will apply a small holding torque to capstan 78 to move the frameassembly 37 firmly against frame side 76. In this position, the opticalsensor 82 will be just to the right of end point indexing slot 85 (FIG.4). Of course, the picker assembly 36 could be returned back to itsoriginal position in essentially the same manner. The combination of theoptical sensor 82, slot aperture 84, and the respective end pointindexing slots 83 and 85, thus provide a means for determining theposition of the picker frame assembly 36 without reference to the motorand drive cable assembly 70.

It is contemplated that the inventive concepts herein described may bevariously otherwise embodied and it is intended that the appended claimsbe construed to include alternative embodiments of the invention exceptinsofar as limited by the prior art.

What is claimed is:
 1. Apparatus for linearly displacing a roboticpicker assembly along a lateral axis and for supporting the roboticpicker assembly at a fixed orientation relative to a horizontalreference plane and at predetermined points along the lateral axis, therobotic picker assembly having a front end, a rear end, and two opposedsides, comprising:a support frame having a front end, a rear end, andtwo opposed sides, the front and rear ends being generally parallel tothe lateral axis, and the two opposed sides being generally parallel toa longitudinal axis, the lateral and longitudinal axes lying within thehorizontal reference plane, said support frame including a firstelongate bearing surface located at about the front end of said supportframe and extending between the two opposed sides, said first elongatebearing surface extending in a direction that is substantially parallelto the lateral axis and lying in a first bearing surface plane that issubstantially parallel to the horizontal reference plane; and a secondelongate bearing surface located at about the rear end of said supportframe and extending between the two opposed sides, said second elongatebearing surface extending in a direction that is substantially parallelto the lateral axis and lying in a second bearing surface plane that issubstantially parallel to the horizontal reference plane, the secondbearing surface plane being non-coplanar with said first bearing surfaceplane; a three point contact primary bearing assembly mounted to therobotic picker assembly and engaging said first and second elongatebearing surfaces, said three point contact primary bearing assemblyallowing the robotic picker assembly to be displaced within said supportframe in a direction generally parallel to the lateral axis; and anactuator connected to the robotic picker assembly for linearlytranslating the robotic picker assembly to predetermined points alongthe lateral axis.
 2. The apparatus of claim 1, further comprising:athird elongate bearing surface extending between the two opposed sides,said third elongate bearing surface extending in a direction that issubstantially parallel to the lateral axis and lying in a third bearingsurface plane that is substantially perpendicular to the horizontalreference plane; a fourth elongate bearing surface extending between thetwo opposed sides, said fourth elongate bearing surface extending in adirection that is substantially parallel to the lateral axis and lyingin a fourth bearing surface plane that is substantially perpendicular tothe horizontal reference plane, the third bearing surface plane beingnon-coplanar with the fourth bearing surface plane; and a three pointcontact secondary bearing assembly mounted to the robotic pickerassembly and engaging said third and fourth elongate bearing surfaces,said three point contact secondary bearing assembly preventing therobotic picker assembly from being displaced in a direction generallyparallel to the longitudinal axis.
 3. The apparatus of claim 2, whereinsaid three point contact primary bearing assembly comprises:a firstpoint contact bearing mounted to the front end of the robotic pickerassembly near one of the two opposed sides; a second point contactbearing mounted to the front end of the robotic picker assembly near theother of the two opposed sides, said first and second point contactbearings engaging said first elongate bearing surface; and a third pointcontact bearing mounted to the rear end of the robotic picker assemblyand engaging said second elongate bearing surface.
 4. The apparatus ofclaim 3, wherein said second elongate bearing surface is elevated withrespect to said first elongate bearing surface.
 5. The apparatus ofclaim 4, wherein said three point contact secondary bearing assemblycomprises:a fourth point contact bearing mounted to the rear end of therobotic picker assembly near one of the two opposed sides; a fifth pointcontact bearing mounted to the rear end of the robotic picker assemblynear the other of the two opposed sides, said fourth and fifth pointcontact bearings engaging said third elongate bearing surface; and asixth point contact bearing mounted to the rear end of the roboticpicker assembly between said fourth and fifth point contact bearings,said sixth point contact bearing engaging said fourth elongate bearingsurface.
 6. The apparatus of claim 5, wherein said sixth point contactbearing is biased against.
 7. The apparatus of claim 6, furthercomprising position encoder means connected to the robotic pickerassembly for determining a position of the robotic picker assembly alongthe lateral axis.
 8. The apparatus of claim 7, wherein said positionencoder means comprises:position indexing means attached to said supportframe for providing a plurality of fixed indexing points; and detectormeans attached to the robotic picker assembly for detecting theplurality of fixed indexing points.
 9. The apparatus of claim 6, whereinsaid first, second, third, fourth, fifth, and sixth point contactbearings comprise rollers.
 10. The apparatus of claim 1, wherein saidactuator comprisesa drive motor mounted to the robotic picker assembly,said drive motor having an output shaft; a capstan mounted the outputshaft of said motor; an elongate flexible tension member having a firstend and a second end, the first end of said elongate flexible tensionmember being attached to one of the two opposed sides of said supportframe, the second end of said elongate flexible tension member beingattached to the other of the two opposed sides of said support frame,said elongate flexible tension member also being wrapped at least oncearound said capstan so that said elongate flexible tension member is infrictional engagement with said capstan.
 11. The apparatus of claim 10,wherein said elongate flexible tension member comprises a wire rope. 12.The apparatus of claim 11, further comprising a tensioner memberconnected to one end of the wire rope, wherein said tensioner membermaintains the wire rope at a predetermined tension.
 13. Apparatus forlinearly displacing a robotic picker assembly along a lateral axis andfor supporting the robotic picker assembly at a fixed orientationrelative to a horizontal reference plane and at predetermined pointsalong the lateral axis, the robotic picker assembly having a front end,a rear end, and two opposed sides, comprising:a support frame having afront end, a rear end, and two opposed sides, the front and rear endsbeing generally parallel to the lateral axis, and the two opposed sidesbeing generally parallel to a longitudinal axis, the lateral andlongitudinal axes lying within the horizontal reference plane; a firstpoint contact bearing mounted to the front end of the robotic pickerassembly near one of the two opposed sides; a second point contactbearing mounted to the front end of the robotic picker assembly near theother of the two opposed sides, said first and second point contactbearings engaging a front end horizontal bearing surface on said supportframe, the front end horizontal bearing surface being contained withinthe horizontal reference plane; a third point contact bearing mounted tothe rear end of the robotic picker assembly and engaging a rear endhorizontal bearing surface on said support frame, the rear endhorizontal surface being substantially parallel to the horizontalreference plane and elevated with respect to the horizontal referenceplane; a fourth point contact bearing mounted to the rear end of therobotic picker assembly near one of the two opposed sides; a fifth pointcontact bearing mounted to the rear end of the robotic picker assemblynear the other of the two opposed sides, said fourth and fifth pointcontact bearings engaging a first side of a vertical bearing surface onsaid support frame, the vertical bearing surface being perpendicular tothe horizontal reference plane; a sixth point contact bearing mounted tothe rear end of the robotic picker assembly between said fourth andfifth point contact bearings, said sixth point contact bearing engaginga second side of the vertical bearing surface, the second side of thevertical bearing surface being opposed to the first side, said sixthpoint contact bearing being biased against the second side of thevertical bearing surface; actuating means connected to the roboticpicker assembly for linearly translating the robotic picker assembly topredetermined points along the lateral axis; position encoder meansconnected to the robotic picker assembly for determining a position ofthe robotic picker assembly along the lateral axis, said positionencoder means including:position indexing means attached to said supportframe for providing a plurality of fixed indexing points, wherein saidposition indexing means comprises an aperture having a first end and asecond end and a first end point indexing slot positioned a spaceddistance from the first end of said aperture, and a second end pointindexing slot positioned a spaced distance from the second end of saidaperture; and detector means attached to the robotic picker assembly fordetecting the plurality of fixed indexing points.
 14. The apparatus ofclaim 13, wherein said detector means comprises an optical sensor.
 15. Acartridge engaging assembly, comprising:a support frame having a front,a rear, and two opposed sides, said support frame including a base platethat defines a horizontal reference plane, the front and rear sidesbeing generally parallel to a lateral axis, and the two opposed sidesbeing generally parallel to a longitudinal axis, said support frameincludinga first elongate bearing surface located at about the front endof said support frame and extending between the two opposed sides, saidfirst elongate bearing surface extending in a direction that issubstantially parallel to the lateral axis and lying in a first bearingsurface plane that is substantially parallel to the horizontal referenceplane; a second elongate bearing surface located at about the rear endof said support frame and extending between the two opposed sides, saidsecond elongate bearing surface extending in a direction that issubstantially parallel to the lateral axis and lying in a second bearingsurface plane that is substantially parallel to the horizontal referenceplane, the second bearing surface plane being non-coplanar with saidfirst bearing surface plane; a third elongate bearing surface extendingbetween the two opposed sides, said third elongate bearing surfaceextending in a direction that is substantially parallel to the lateralaxis and lying in a third bearing surface plane that is substantiallyperpendicular to the horizontal reference plane; and a fourth elongatebearing surface extending between the two opposed sides, said fourthelongate bearing surface extending in a direction that is substantiallyparallel to the lateral axis and lying in a fourth bearing surface planethat is substantially perpendicular to the horizontal reference plane,the third bearing surface plane being non-coplanar with the fourthbearing surface plane; a robotic picker assembly having a front, a rear,and two opposed sides; a first point contact bearing mounted to thefront of said robotic picker assembly near one of the two opposed sides,said first point contact bearing engaging said first elongate bearingsurface; a second point contact bearing mounted to the front of saidrobotic picker assembly near the other of the two opposed sides, saidsecond point contact bearing engaging said first elongate bearingsurface; a third point contact bearing mounted to the rear of saidrobotic picker assembly, said third point contact bearing engaging saidsecond elongate bearing surface; a fourth point contact bearing mountedto the rear of said robotic picker assembly near one of the two opposedsides, said fourth point contact bearing engaging said third elongatebearing surface; a fifth point contact bearing mounted to the rear ofsaid robotic picker assembly near the other of the two opposed sides,said fifth point contact bearing engaging said third elongate bearingsurface; a sixth point contact bearing mounted to the rear of saidrobotic picker assembly between said fourth and fifth point contactbearings, said sixth point contact bearing engaging said fourth elongatebearing surface; and an actuator connected to the robotic pickerassembly for linearly translating the robotic picker assembly topredetermined points along the lateral axis.